The present invention relates in general to shifting mechanisms for vehicle transmissions and in particular to an improved interlock assembly for preventing more than one of a plurality of shift bars within a transmission shifter &0 assembly from being moved out of a central neutral position at a given time.
In a typical multiple speed vehicle transmission, a shifter assembly is used for selecting a desired one of a plurality of gear ratios between an input shaft and an output shaft. A plurality of shift bars are provided within the shifter assembly for accomplishing this gear ratio selection. If, for example, the transmission is capable of five forward gear ratios and one reverse gear ratio, the shifter assembly usually includes three of such shift bars. The shift bars are typically oriented in parallel fashion adjacent to one another, each being supported for longitudinal movement in opposite directions from a central neutral position. Thus, each of the three shift bars is capable of being moved to two different gear engaging positions within the shifter assembly for use.
The shifter assembly further includes a gear shift lever, the upper end of which is manually operable by an operator of the vehicle. The lower end of the gear shift lever extends into the shifter assembly so as to cooperate with aligned notches formed on each of the shift bars. By moving the upper end of the shift lever about a first axis of movement (the selecting axis), the operator can move the lower end thereof into a single desired one of the aligned notches formed in the shift bars. This selecting movement of the shift lever does not move any of the shift bars out of their central neutral positions, but rather selects one of the shift bars for such movement. The operator can then actually move the selected shift bar out of its central neutral position into one of the two gear engaging positions by moving the upper end of the shift lever about a second axis of movement (the shifting axis). Generally, the shifting axis is transverse to the selecting axis.
Severe damage may occur to the components of the transmission if more than one of the shift bars is moved out of the central neutral position at any given point in time. Thus, it is important that the shifter assembly include some means for preventing this from occurring. To this end, it is known to provide an interlock assembly which, when one of the shift bars is initially selected for movement as described above, mechanically engages the other shift bars so as to prevent any movement thereof out the their central neutral positions.
Damage may also occur to the transmission if the shift bars are not moved in accordance with a predetermined sequence, i.e. if the gear ratios of the transmission are not properly selected. Such improper selection may occur inadvertently if the operator of the vehicle incorrectly moves the shift lever about the selecting axis. This situation occurs because the operator does not look down to visually determine the position of the shift lever, but rather relies upon the "feel" thereof when moving the shift lever. In the past, spring loaded mechanisms have been used in conjunction with the shift lever to provide tactile feedback to the operator as to the position thereof. Such mechanisms have also been provided to urge the shift lever toward a centered position relative to the shift bars. Unfortunately, such mechanisms have also been relatively complicated and expensive to manufacture.